KR20090114437A - Linear machine having a primary part and a secondary part - Google Patents

Abstract

The invention relates to a linear machine having a primary part (20), which forms a holder (11) about an axis A and comprises a plurality of annular primary coils (21) for generating a magnetic field in the holder (11), wherein the primary coils are disposed concentrically to the axis A, can be supplied with alternating current and spaced by intermediate elements (22), and having a secondary part (30), which can be moved relative to the primary part (20) through the magnetic field in the holder (11) along the axis A and is provided with secondary coils (31) comprising superconductor windings. In order to create a linear motor that enables high power densities, the intermediate elements (22) are made of non-magnetizable material, and the primary coils (21) and secondary coils (31) are arranged with air gap windings, wherein the secondary coils (31) are made of a high-temperature superconductor and direct current can be or is applied to them. With the linear motors, power densities of more than 18 N/cm2 are achieved in the holder (11).

Description

LINEAR MACHINE HAVING A PRIMARY PART AND A SECONDARY PART}

The invention preferably comprises a primary portion with a plurality of ring-shaped primary coils arranged concentrically about the axis and spaced from each other by an intermediate member, and axially alternating with alternating polarity with direct current applied and superconducting windings. And a secondary part having a plurality of secondary coils arranged side by side, wherein one part is capable of reciprocating parallel to the axis with respect to the other part.

In DE 195 42 551 A1 a linear motor with a hollow cylindrical primary part is known. The primary portion has a ring-shaped primary coil disposed concentrically about the axis of motion of the secondary portion and operable with a polyphase current. Ring-shaped sheets of soft magnetic material are disposed between the primary coils, which are used as intermediate members for the separation of adjacent primary coils and form magnetizable teeth, thereby increasing the magnetic flux and Guided to the arranged receiving portion. Primary coils and ring-shaped sheets are housed in a hollow cylindrical yoke made of magnetizable material, the yoke forming a back iron. The secondary part is disposed movably in the axial direction inside the receiving portion formed as the primary part. The secondary part has multiple fields consisting of superconducting windings. The fields are arranged in sequence axially with alternating polarities. In DE 195 42 551 the magnetic field of the secondary winding must be perpendicular to the axis of the secondary part. In order to generate this magnetic field direction by the winding coils, the axis of the individual coil through which the current flows must be perpendicular to the axis of motion of the linear motor. Only when using permanent magnets or superconducting solid magnets, the inner circumferential surface of the magnets can contact the cylindrical yoke made of magnetizable material. The magnets are embodied in a ring but are magnetized in the radial direction. Alternatively, in the case of wound secondary coils, the wound coils should be arranged such that they are offset side by side in the circumferential and axial directions on the outer surface of the support. The magnetic force generated when current is applied to the primary and secondary coils generates a relative motion between the primary and secondary portions.

In EP 1 465 328 A1 a linear motor is known, in which the primary part and the secondary part are arranged in reverse, whereby the secondary part is placed outside and surrounding the primary part.

The magnetization potential of the soft magnetic teeth is limited due to the magnetic saturation of the soft magnetic material. In order to obtain higher power density between the primary and secondary parts when the current density in the coil of the primary part is high, it has been proposed to increase the number of windings of the primary coils or increase the amount of magnetizable material. . In the experimental stage, for circular or polysolenoid linear motors, this measure yielded a power density of up to about 8 N / cm 2. However, the size and weight of the linear motor must be much larger.

It is an object of the present invention to provide a linear machine, by means of structural measures in the primary and / or secondary parts, where a much higher power density can be obtained while the size of the linear machines is small.

The object is realized according to the invention as an air gap winding in which the placement of primary coils in the primary part comprises intermediate members of a non-magnetizable material, wherein the secondary coils are made of windings of high temperature superconductor, thereby providing 18 N / A power density greater than 2 cm 2 is achieved. The linear machine is preferably embodied as a linear motor in which current is applied to the primary and secondary coils so that the relative motion between the primary and secondary parts is caused parallel to the axis by the resulting magnetic field, and the present invention This is described below in this regard. The linear machine can also be implemented as a generator in which the current induced into the primary coils by the relative motion between the primary and secondary parts is converted for generation. High power density is achieved by applying alternating current to the primary coil and direct current to the secondary coil when the linear machine is designed as a linear motor. Since the arrangement of the primary coils and preferably the arrangement of the secondary coils are also carried out with air gap windings, ie no magnetizable material for the magnetic flux guide is disposed between the primary coils and between the secondary coils. In linear machines, the power density is not limited by saturation magnetization.

Since the current distribution of the primary portion, i.e. the current in the circumferential direction per axial length of the primary portion, can be larger than the known linear motor without increasing the size of the linear motor, the power density proportional to the current distribution is saturated. It grows without effect. There is preferably no magnetizable material or iron for bundling magnetic flux between the primary coils. By using secondary coils made of a high temperature superconducting material in the secondary portion, having a transition temperature higher than 77K, a high direct current can be applied to the secondary coils, so a very strong magnetic field can occur in the receiving portion. Another advantage of the linear motor according to the invention is that an almost smooth power curve in the axial direction is obtained, because cogging rarely occurs since practically no magnetic reluctance is produced by the air gap winding. In addition, since the permanent magnet and the magnetizable material are omitted in the primary part and the secondary part, no magnetic force is generated when the current supply is interrupted, so that the linear motor can be maintained or cleaned relatively simply.

The high current distribution of the primary part can be achieved, in particular, by the high selection of the charge factor of the primary part. The charge factor is defined as the volume ratio of the volume of the primary coil to which the current flows to the intermediate member and, in some cases, the volume of the intermediate space between the primary coils present. The filling factor of the primary portion is preferably greater than 70%, in particular greater than 85%. An alternating current, preferably phase shifted by 120 °, is applied to the primary coils adjacent in the axial direction, so that the linear motor forms a three-phase motor (recurrent current motor). For two-phase motors or multiphase motors with more than three phases, the phase shift can be adjusted or selected otherwise.

In a preferred embodiment, the primary coil has a winding made of a standard conductor, in particular a conductor made of aluminum or copper, so that the primary coils can be liquid cooled or gas cooled, for example at reasonable costs. Particular preference is given to cooling with water or oil, for example. Standard conductors may in particular be made of hollow conductors, the inner tube of which is used for cooling. As an alternative, the windings of the primary coils can be made or made of a superconducting, in particular high temperature superconducting conductor. The current application should consist of alternating current with a frequency lower than 100 Hz, in particular less than 50 Hz, so that the alternating current losses in the superconducting primary coils are small. Otherwise, the alternating current losses will have to be compensated for by further cooling. In the linear generator according to the present invention, a power density greater than 18 N / cm 2 can be obtained, and a power density greater than 25 N / cm 2 can be obtained when superconductors are used in the secondary coil and the primary coil. For cooling of the primary coils, a cooling line can be formed between the coils through which coolant can flow, or a gap can be provided between the primary coils and optionally intermediate members. The intermediate members may be formed in a ring segment shape, whereby the coolant may reach the end face of the primary coil not covered by the ring segment. The intermediate members may extend in their entirety, in part or in intermediate spaces, over the radial height of the primary coil. The intermediate members may be of a lattice structure, hollow body or sliding body, having sufficient mechanical stability and allowing coolant flow.

More preferably the primary and secondary coils are surrounded by a yoke, which yoke is preferably made of a non-magnetizable material, in particular a light material without iron. As an alternative, the yoke can be made of an iron containing and / or magnetizable material for magnetic field shielding. The yoke and intermediate members form a mechanical support skeleton, in particular for the primary coil. In order to fix the intermediate members in the axial direction, the yoke has a groove on its inner circumference, and the intermediate members engage into the shape coupling manner into the groove. By fixing the intermediate members to the yoke, the primary coils can be supported by the intermediate members in the axial direction, so that the yoke can absorb the magnetic force acting on the primary coils in the axial direction. In order to avoid the saturation effect and at the same time obtain a particularly light configuration of the primary part and the linear machine, it is particularly preferred that the primary part be formed without iron. Alternatively, the yoke may include a magnetizable material for feedback of the magnetic flux.

The primary coil can be cast into a plastic, preferably a synthetic resin, in particular an epoxy resin. In a preferred embodiment of the invention, the intermediate members are also made of plastics, preferably synthetic resins, in particular epoxy resins, and can be fiber reinforced, for example by insertion of glass fiber materials.

Superconducting secondary coils can deliver high current densities, preferably greater than 50 A / mm 2, more preferably greater than 70 A / mm 2, in particular greater than 100 A / mm 2, so that the secondary coil Very large magnetic fields can be formed. The magnetic flux density that may be formed by the secondary portion may be greater than 0.5 Tesla, preferably greater than 1 Tesla, and in some cases up to 2 Tesla in the air gap. The secondary part preferably comprises a cylindrical support, on which the secondary coil is arranged. The support of the secondary part is preferably made of a nonmagnetic material, for example made of fiber reinforced plastic. The support may be made or made of magnetic material, such as iron. In an embodiment, the secondary coil is formed in a ring shape and fixedly disposed on the corresponding support of the secondary part concentrically about the axis. Secondary coils adjacent in the axial direction are supplied with direct current in reverse by means of a reverse pole connection during operation. Non-magnetizable ring-shaped spacers can be arranged between the secondary coils to implement air gap windings, in which the secondary coils are axially supported. In this embodiment, adjacent secondary coils are spaced from each other, the spacing being greater than twice the axial width of each secondary coil. In addition, multiple coils all connected in the same current flow direction (connected in series or in parallel) may be integrated to form one packet. In this case, opposite coil currents are applied to adjacent coil packets, respectively.

Other advantages and features of the present invention are described below in connection with an embodiment of a linear motor as a linear machine, schematically illustrated in the figures.

1 is a linear motor according to the invention comprising a primary part and a secondary part of a first embodiment,

FIG. 2 is a perspective view of the secondary portion of FIG. 1. FIG.

1 shows a linear motor 10 comprising a primary portion 20 and a secondary portion 30. The primary portion 20 defines a cylindrical receiving portion 11 in which the secondary portion 30 is placed reciprocally along the central axis A. The primary part 20 comprises five primary coils 21 arranged concentrically about the axis A in the illustrated embodiment. Only some of the total motors are shown in the figure, for example in the three phase mode the number of coils or coil packets should be a multiple of three. Since the primary coils 21 are made of ring disk coils, an alternating current or rotational flow (three-phase current) of 120 ° phase shift, for example, may be applied to the outer circumference of the ring disk coils through a contact not shown. A moving magnetic field is generated in the accommodating portion 11 by the primary coils 21. Windings made of copper conductors of the primary coil 21 are cast into an epoxy resin for mechanical stabilization. Ring-shaped intermediate members 22 are disposed between the primary coils 21, and end surfaces of the primary coils 21 are supported in the axial direction to the intermediate members. The intermediate members 22 extend radially from the inner circumference of the primary coil 21 to the outer circumference of the primary coils 21. A hollow cylindrical yoke 23 is in contact with the outer circumference of the intermediate members 22 and the primary coils 21, and the intermediate members 22 are fixed to the yoke (not shown). Thus, the yoke 23 and the intermediate members 22 form a mechanical support skeleton for receiving the primary coil 21.

The yoke 23 around the primary portion 20 may be made of a non-magnetizable material or may be made of a magnetizable material for shielding. In the latter case, an increase in power density may appear. If the yoke 23 is made of a conductive material, the yoke may be formed of a material that is preferably sheeted and slotted to reduce alternating current losses.

Since the intermediate member 22 may be made of glass fiber reinforced plastic, for example, and thus cannot be magnetized according to the present invention, the magnetic field generated in the accommodating portion 11 when the current is applied to the primary coils 21 may be the intermediate members ( It is not limited by the saturation magnetization of 22). There is no magnetizable material for the magnetic flux guide between the primary coils 21. Therefore, the arrangement of the primary coils 21 arranged next to each other in the axial direction is implemented by so-called air gap windings. The "air gap" between the primary coils 21 is in some cases filled with intermediate members 22 which are only partially used for hollow and / or insulation. Thus, within the primary portion 20 a very wide primary coil 21 with a large number of windings per axial length can be used. Since the volume of the intermediate members 22 occupies only a part of the volume of the primary coils 21, the charge factor of the primary part by windings that carry current and generate a magnetic field (moving magnetic field) is 50%. Much larger than As such, a higher current can be provided in the primary coils 21 of the primary portion 20.

The secondary portion 30 shown in FIGS. 1 and 2 has ring-shaped secondary coils 31 made of a high temperature superconductor, arranged concentrically about the axis A. FIG. Direct current is applied to the superconducting secondary coils 31 at cryogenic temperatures greater than 20K, and the secondary coils 31 adjacent in the axial direction are connected in reverse phase. The high temperature superconductor windings or secondary coils 31 in the secondary portion 30 may be implemented as pancake-coils, double pancake-coils, as packets of the pancake-coils or as short solenoid coils. Between the secondary coils 31 are arranged ring-shaped spacers 32 arranged concentrically about the axis A. The spacers 32 are made of glass fiber reinforced epoxy resin and are disposed on the hollow cylindrical support tube 33 together with the secondary coils 31. The hollow cylindrical support tube 33 may be made of soft magnetic, magnetizable material, such as soft magnetic iron, or may be made of, for example, glass fiber reinforced plastic. In order to cool the secondary coils 31 with liquid nitrogen, for example, a cryostat 34 is provided with a double walled tube 36. An unshown intermediate space between the "warm" outer tube wall and the "cold" inner tube wall of the tube 36 is evacuated to prevent or reduce heat transfer from the outside to the cryostat 34. In some cases, an insulating layer consisting of a commercially available super insulating film may be attached around the cold tube wall. The force transfer from the secondary portion 30 to the cryostat 34 is effected by the transmission members 35a, 35b schematically shown. The transfer members 35a and 35b are made of a material having low thermal conductivity and high mechanical strength, such as glass fiber reinforced plastic. The secondary coils 31 can be operated at current densities up to 100 A / mm 2. The linear motor 10 comprising a primary part 20 implemented according to the invention with an air gap winding of the primary coils, and a secondary part 30 constructed according to the invention, comprises a primary part and a secondary part. By obtaining a power density larger than 18 N / cm 2 in the accommodating portion 11, the secondary portion 30 is moved in parallel with the axis A. FIG.

Those skilled in the art can obtain many variations from the foregoing description and the dependent claims. The number of primary coils and secondary coils in the axial direction is exemplary only and may vary in particular depending on the width of the coils and the total length of the linear motor. The secondary coil may also be arranged in a helical manner. The support tubes of the yoke and the secondary part may also consist of iron-containing material. If the secondary coils are coupled with the spacers, for example by vacuum impregnation, the support tube for the secondary part can be omitted. As an alternative, the support tube for the secondary part may be made of a magnetizable material or a fibre-reinforced plastic, which is sheeted and has a slot. The ferromagnetic material can be used as a support tube in the secondary portion where direct current flows. In particular, when using standard conductive primary coils, the cooling of the primary coils may be indirectly or preferably directly, for example by water, oil, gas or nitrogen (N ₂ ). Alternatively, suitable gas cooling or dry cooling may be achieved which allows for operating temperatures of less than 77K, such as 20K or 30K. In order to further reduce the eddy current loss in the primary part, a litz wire winding can be provided in the primary coil. In some cases, in order to further increase the power density, a second primary part may be disposed inside the secondary part. Instead of the secondary part, the primary part may be moved parallel to the axis by a magnetic field generated upon application of current. The primary part may be disposed inside, and the secondary part may be disposed outside. If the linear machine is formed as a generator, the secondary part to which direct current is applied can be moved mechanically, for example by buoys that rise and fall of the wave generator. By this movement of the secondary part the current induced in the primary coils of the primary part can be used for power generation, and then the linear machine acts as a generator. Instead of the secondary portion, the primary portion may reciprocate parallel to the axis when the secondary portion is fixed, without departing from the protection scope of the claims.

Claims (19)

Primary part 20 having a plurality of ring-shaped primary coils 21 arranged concentrically about axis A and spaced apart from each other by intermediate member 22, and direct current can be applied and superconducting winding And a secondary portion 30 having a plurality of secondary coils 31 arranged side by side in the axial direction with alternating polarities, one of the two portions being parallel to the axis with respect to the other portion. In a linear machine that can move, The placement of the primary coils 21 in the primary portion 20 is carried out as an air gap winding with intermediate members 22 made of non-magnetizable material, wherein the secondary coils 31 are high temperature superconductors. By the winding of, power density greater than 18 N / cm 2 can be obtained, the secondary coils 31 are formed in a ring shape and are arranged concentrically with each other around the support 33, and the secondary coils Linear machines, characterized in that between the (31) are arranged spacer members in which the secondary coils (31) are axially supported. The method of claim 1, Linear machine, characterized in that the placement of the secondary coils (31) in the secondary part (20) is carried out as an air gap winding. The method according to claim 1 or 2, Between the primary coils 21 of the primary part 20 and the secondary coils 31 of the secondary part 30 that no magnetizable material, in particular iron, for bundling magnetic flux is disposed Characterized by linear machine. The method according to any one of claims 1, 2 or 3, A linear, characterized in that the filling factor of the primary portion 20, defined as the volume ratio of the primary coils 21 to the intermediate members 22 and / or intermediate spaces, is greater than 70%, in particular 85% machine. The method according to any one of claims 1 to 4, Said primary coils (21) consist of windings of standard conductors, in particular windings of conductors or hollow conductors of aluminum or copper. The method according to any one of claims 1 to 4, Wherein said primary coils are made of windings of superconductor, preferably high temperature superconductor. The method according to any one of claims 1 to 6, The yoke (32) surrounding the primary coils (21) and the intermediate members (22) is preferably made of a nonmagnetic material or a non-magnetizable material, in particular a light constituent material. The method of claim 7, wherein The yoke has, on the inner circumference, grooves in which the intermediate members (22) are fixed. The method according to any one of claims 1 to 8, The primary coils 21 and / or the secondary coils 31 are cast into a plastic, preferably a synthetic resin, in particular an epoxy resin, wherein the intermediate members are partly or completely made of a plastic sheath. Linear machine. The method according to any one of claims 1 to 9, A current density greater than 50 A / mm 2, preferably 70 A / mm 2, particularly preferably 100 A / mm 2, is applicable or applied to the secondary coils 31 and / or the magnetic field of the secondary coils 31. Linear machine, characterized in that it is oriented parallel to the axis. The method according to any one of claims 1 to 10, The secondary part comprises a cylindrical support (33), characterized in that the secondary coils (31) are arranged on the outer circumferential surface of the support. The method of claim 11, The support (33) is a linear machine, characterized in that made of a non-magnetic or non-magnetizable material. The method according to any one of claims 1 to 12, Linear machine, characterized in that the spacers (32) are formed of a non-magnetizable or non-magnetizable material. The method of claim 13, The spacing between adjacent secondary coils (31) corresponds to at least twice the width of the secondary coils (31). The method according to any one of claims 1 to 14, Alternating current may be applied to or applied to the primary coils, and current is applied to the primary and secondary coils 21 and 31 so that the primary and secondary portions 20 and 30 are relative to each other. The linear machine, characterized in that it is movable and said linear machine forms a linear motor (10). The method of claim 15, Said primary coils are made of superconductor, preferably high temperature superconductor, and alternating current is applied at a frequency of less than 100 Hz, in particular less than 50 Hz. The method according to any one of claims 1 to 16, The primary portion or the secondary portion is movable externally parallel to the axis, and the current induced by the axial movement between the primary portion and the secondary portion within the primary coil can be tapped. And the linear machine forms a generator. Claims 1 to 9, 16 or 17 comprising a plurality of ring-shaped primary coils 21, arranged concentrically about axis A and spaced apart by intermediate members 22. In the primary part of a linear machine according to any one of the following, The placement of the primary coils 21 in the primary portion 20 is carried out as an air gap winding with intermediate members 22 made of non-magnetizable material, alternating with the primary coils arranged next to each other. The primary part of the linear mechanical part, characterized in that the phase shift can be applied. In the secondary part of the linear machine according to any one of claims 1 to 9, comprising a plurality of secondary coils 31 having a superconductor winding and arranged axially side by side, The arrangement of the secondary coils 31 is carried out as an air gap winding, and the secondary coils 31 are made of a high temperature superconductor and direct current can be applied with opposite polarity to the secondary coils arranged side by side. Secondary part of a linear machine.

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